Some conventional optical-disc-based optical analyzers use a playback function of an optical disc device to trace a sample under test provided on a certain part of an optical disc by using a laser to obtain an image of the traced sample. (See Japanese Unexamined Patent Publication No. 10-504397, for example.)
An optical disc 101 has a track 103 in an aluminum reflecting layer formed on the surface of a substrate 102 and information is recorded on the track 103 as microscopic pits or wobble grooves 104, as shown in FIGS. 10 and 11. Reference numeral 105 indicates a protective layer.
In conventional optical disc units, information on a track 103 is read by using laser light Ph from a pick-up 107 while the optical disc 101 is being rotated in the direction indicated by arrow C by a disc motor 106 as shown in FIG. 12. The pick-up 107 engages a lead screw 109 which is driven by a traverse motor 108. A servo control circuit 110 drives the traverse motor 108 to move the pick-up 107 radially according to reproduction outputs from the pick-up 107 so that the pick-up follows and traces the track 103. The servo control circuit 110 also detects address information recorded on the track 103 and CLV-controls (Constant-Linear-Velocity-controls) the disc motor 106 so that a constant linear velocity is maintained.
More specifically, the position irradiated with the laser light Ph on the optical disc 101 is controlled by the traverse motor 108 and the light path of the laser light Ph is also controlled in the direction of the surface of the optical disc 101 by a tracking actuator (not shown) provided inside the pick-up 107 as required so that the track 103 is accurately traced.
The configuration described so far is the same as that of typical optical disc units for conventional audio or video optical discs. Unlike audio and video discs, an analyzing optical disc 101 has a sample 111 provided on it as shown in FIGS. 10 and 11. Optical analyzers have a photodetector (hereinafter referred to as PD) provided in the pick-up 107, in addition to the components of the optical disc unit for audio or video optical discs, which reads light reflected from the sample 111. The reflected light is processed by a video signal processing circuit 112 to obtain the image of the sample 111.
In the example described above, light reflected from an optical disc 101 is read and analyzed. If a sample 111 is to be analyzed by observing light transmitted through the optical disc, the PD is provided above the optical disc 101.
In such an optical analyzer, a laser with the same wavelength outputted from the optical pick-up 107 is used for both reading the track and analyzing a sample. Because a laser emitted from a single light source is used and the information recorded as pits or wobble grooves on the disc must be accurately read and traced, the laser used for analysis cannot be adjusted so as to emit light having a wavelength other than the wavelength for reading the pits or wobbles on the disc.
The inventers have been conducting studies and found that a laser wavelength (780 nm) for detecting pits and wobble grooves is not necessarily most suitable for capturing the image or light and shade of a part in which a sample is provided.
For example, if absorptiometric analysis is used for analyzing samples, it is advantageous to use the maximum absorption wavelength of the samples to be analyzed. Therefore, a light source is needed that can generate a wide range of wavelengths in order to conduct analysis of various types of samples on a single analyzer. For example, potassiumpermanganate solutions absorb light of wavelengths between 525 to 545 nm best. That is, they are the maximum absorption wavelengths for the solutions. In that case, almost all light with a wavelength of 700 nm pass through these solutions.
A water soluble formazan commonly called WST-3 (manufactured by DOJINDO laboratories), which is generated from a tetrazolium salt reduced by NADH exhibits the highest absorbance at a maximum absorption wavelength of 433 nm. Also this solution absorbs almost no light having wavelengths of 600 nm or more. Therefore, it is disadvantageous for high-precision measurement to use a single wavelength to conduct absorption analysis of different substances having different absorption spectra.
The turbidity of a sample can be cancelled by using the difference between the absorbance of the sample at its maximum absorption wavelength and the absorbance at a wavelength substantially different from the wavelength. However, under present circumstances, analysis in which turbidities are canceled cannot be conducted because present-day optical analyzers can output only a single laser wavelength.
An object of the present invention is to provide an optical analyzer suitable for obtaining information from pits or wobble grooves on an optical disc as well as for obtaining the image of a sample portion and detecting calorimetric information about the sample, such as light and shade or the absorbance of the sample.